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zsh/Src/Modules/random.c
2024-08-31 17:22:02 +02:00

326 lines
7.4 KiB
C

/*
* random.c - module to access kernel random sources.
*
* This file is part of zsh, the Z shell.
*
* Copyright (c) 2022 Clinton Bunch
* All rights reserved.
*
* Permission is hereby granted, without written agreement and without
* license or royalty fees, to use, copy, modify, and distribute this
* software and to distribute modified versions of this software for any
* purpose, provided that the above copyright notice and the following
* two paragraphs appear in all copies of this software.
*
* In no event shall Clinton Bunch or the Zsh Development Group be liable
* to any party for direct, indirect, special, incidental, or consequential
* damages arising out of the use of this software and its documentation,
* even if Clinton Bunch and the Zsh Development Group have been advised of
* the possibility of such damage.
*
* Clinton Bunch and the Zsh Development Group specifically disclaim any
* warranties, including, but not limited to, the implied warranties of
* merchantability and fitness for a particular purpose. The software
* provided hereunder is on an "as is" basis, and Clinton Bunch and the
* Zsh Development Group have no obligation to provide maintenance,
* support, updates, enhancements, or modifications.
*
*/
#include "random.mdh"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdint.h>
#ifdef HAVE_SYS_RANDOM_H
#include <sys/random.h>
#endif
/* Simplify select URANDOM specific code */
#if !defined(HAVE_ARC4RANDOM_BUF) && !defined(HAVE_GETRANDOM)
#define USE_URANDOM
#endif
/* buffer to pre-load integers for SRANDOM to lessen the context switches */
static uint32_t rand_buff[8];
static int buf_cnt = -1;
#ifdef USE_URANDOM
/* File descriptor for /dev/urandom */
int randfd = -1;
#endif /* USE_URANDOM */
static zlong get_srandom(UNUSED(Param p));
/**/
ssize_t
getrandom_buffer(void *buf, size_t len)
{
ssize_t ret;
#ifndef HAVE_ARC4RANDOM_BUF
size_t val = 0;
uint8_t *bufptr = buf;
#endif
do {
errno = 0;
#ifdef HAVE_ARC4RANDOM_BUF
arc4random_buf(buf,len);
ret = len;
#elif defined(HAVE_GETRANDOM)
ret=getrandom(bufptr,(len - val),0);
#else
ret=read(randfd,bufptr,(len - val));
#endif
if (ret < 0) {
if (errno != EINTR || errflag || retflag || breaks || contflag) {
zwarn("Unable to get random data: %e.", errno);
return -1;
}
}
#ifndef HAVE_ARC4RANDOM_BUF
bufptr += ret;
val += ret;
#endif
} while (ret < len);
return ret;
}
/*
* Generate count number of random 32-bit integers between 0 and max-1
* Got this algorithm from
*https://lemire.me/blog/2016/06/30/fast-random-shuffling/
* adapting the public domain code.
*
*/
/**/
void
get_bound_random_buffer(uint32_t *buffer, size_t count, uint32_t max)
{
uint64_t multi_result;
uint32_t threshold;
uint32_t leftover;
size_t i; /* loop counter */
getrandom_buffer((void*) buffer, count*sizeof(uint32_t));
if (max == UINT32_MAX)
return;
for(i=0;i<count;i++) {
multi_result = ((uint64_t) buffer[i]) * (uint64_t) max;
leftover = (uint32_t) multi_result;
/*
* The following if statement should (according to Google's Gemini)
* only be executed with a probability of 1/2**32 or 2.33e-10
*/
if(leftover < max) {
threshold= -max % max;
while (leftover < threshold) {
uint32_t j=get_srandom(NULL);
multi_result=(uint64_t) j * (uint64_t) max;
leftover= (uint32_t) multi_result;
}
}
buffer[i]=multi_result >> 32;
}
}
/*
* Provides for the SRANDOM parameter and returns an unsigned 32-bit random
* integer.
*/
/**/
static zlong
get_srandom(UNUSED(Param pm)) {
if(buf_cnt <= 0) {
getrandom_buffer((void*) rand_buff,sizeof(rand_buff));
buf_cnt=sizeof(rand_buff)/sizeof(rand_buff[0]);
}
return rand_buff[--buf_cnt];
}
/*
* Implements math function zrand_int takes 0 to 3 arguments an upper bound,
* a lower bound and a flag as to whether the range is inclusive or not. The
* default is exclusive. If neither upper or lower is specified this is no
* different than SRANDOM.
*/
/**/
static mnumber
math_zrand_int(UNUSED(char *name), int argc, mnumber *argv, UNUSED(int id))
{
mnumber ret;
uint32_t i;
zlong lower=0, upper=UINT32_MAX,incl=0, diff;
ret.type = MN_INTEGER;
switch (argc) {
case 0: ret.u.l=get_srandom(NULL);
return ret;
break;
case 3: incl = (argv[2].u.l != 0)?1:0;
case 2: lower = argv[1].u.l;
case 1: upper = argv[0].u.l;
default: diff = upper-lower+incl;
}
if (lower < 0 || lower >= UINT32_MAX) {
zwarn("Lower bound (%z) out of range: 0-4294967295",lower);
} else if (upper < lower) {
zwarn("Upper bound (%z) must be greater than Lower Bound (%z)",upper,lower);
} else if (upper < 0 || upper >= UINT32_MAX) {
zwarn("Upper bound (%z) out of range: 0-4294967295",upper);
}
if ( diff == 0 ) {
ret.u.l=upper; /* still not convinced this shouldn't be an error. */
} else {
get_bound_random_buffer(&i,1,(uint32_t) diff);
ret.u.l=i+lower;
}
return ret;
}
/*
* Implements the mathfunc zrand_float and returns a random floating-point
* number between 0 and 1.
*
*/
/**/
static mnumber
math_zrand_float(UNUSED(char *name), UNUSED(int argc), UNUSED(mnumber *argv),
UNUSED(int id))
{
mnumber ret;
double r;
r = random_real();
if (r < 0) {
zwarnnam(name, "Failed to get sufficient random data.");
}
ret.type = MN_FLOAT;
ret.u.d = r;
return ret;
}
static const struct gsu_integer srandom_gsu =
{ get_srandom, nullintsetfn, stdunsetfn };
static struct paramdef patab[] = {
{"SRANDOM", PM_INTEGER | PM_READONLY_SPECIAL | PM_HIDEVAL, NULL,
&srandom_gsu, NULL, NULL, NULL},
};
static struct mathfunc mftab[] = {
NUMMATHFUNC("zrand_float", math_zrand_float, 0, 0, 0),
NUMMATHFUNC("zrand_int", math_zrand_int, 0, 3, 0),
};
static struct features module_features = {
NULL, 0,
NULL, 0,
mftab, sizeof(mftab)/sizeof(*mftab),
patab, sizeof(patab)/sizeof(*patab),
0
};
/**/
int
setup_(UNUSED(Module m))
{
#ifdef USE_URANDOM
/* Check for the existence of /dev/urandom */
struct stat st;
errno=0;
if (stat("/dev/urandom",&st) < 0) {
zwarn("Error getting kernel random pool: %e.", errno);
return 1;
}
errno=0;
if (!(S_ISCHR(st.st_mode)) ) {
zwarn("Error getting kernel random pool: %e.", errno);
return 1;
}
#endif /* USE_URANDOM */
return 0;
}
/**/
int
features_(Module m, char ***features)
{
*features = featuresarray(m, &module_features);
return 0;
}
/**/
int
enables_(Module m, int **enables)
{
return handlefeatures(m, &module_features, enables);
}
/**/
int
boot_(UNUSED(Module m))
{
#ifdef USE_URANDOM
/*
* Open /dev/urandom. Here because of a weird issue on HP-UX 11.31
* When opening in setup_ open returned 0. In boot_, it returns
* an unused file descriptor. Decided against ifdef HPUX as it works
* here just as well for other platforms.
*
*/
int tmpfd=-1;
errno=0;
if ((tmpfd = open("/dev/urandom", O_RDONLY)) < 0) {
zwarn("Could not access kernel random pool: %e.",errno);
return 1;
}
randfd = movefd(tmpfd);
addmodulefd(randfd,FDT_MODULE);
if (randfd < 0) {
zwarn("Could not access kernel random pool.");
return 1;
}
#endif /* USE_URANDOM */
return 0;
}
/**/
int
cleanup_(Module m)
{
return setfeatureenables(m, &module_features, NULL);
}
/**/
int
finish_(UNUSED(Module m))
{
#ifdef USE_URANDOM
if (randfd >= 0)
zclose(randfd);
#endif /* USE_URANDOM */
return 0;
}